When a jet-powered aircraft lands, the landing gear brakes and aerodynamic drag (e.g., flaps, spoilers, etc.) of the aircraft may not, in certain situations, be sufficient to slow the aircraft down in the required amount of runway distance. Thus, jet engines on most aircraft include thrust reversers to enhance the braking of the aircraft. When deployed, a thrust reverser redirects the rearward thrust of the jet engine to a generally or partially forward direction to decelerate the aircraft. Because at least some of the jet thrust is directed forward, the jet thrust also slows down the aircraft upon landing.
Various thrust reverser designs are commonly known, and the particular design utilized depends, at least in part, on the engine manufacturer, the engine configuration, and the propulsion technology being used. Thrust reverser designs used most prominently with jet engines fall into three general categories: (1) cascade-type thrust reversers; (2) target-type thrust reversers; and (3) pivot door thrust reversers. Each of these designs employs a different type of moveable thrust reverser component to change the direction of the jet thrust.
Cascade-type thrust reversers are normally used on high-bypass ratio jet engines. This type of thrust reverser is located on the circumference of the engine's midsection and, when deployed, exposes and redirects air flow through a plurality of cascade vanes. The moveable thrust reverser components in the cascade design includes several translating sleeves or cowls (“transcowls”) that are deployed to expose the cascade vanes.
Target-type reversers, also referred to as clamshell reversers, are typically used with low-bypass ratio jet engines. Target-type thrust reversers use two doors as the moveable thrust reverser components to block the entire jet thrust coming from the rear of the engine. These doors are mounted on the aft portion of the engine and may form the rear part of the engine nacelle.
Pivot door thrust reversers may utilize four doors on the engine nacelle as the moveable thrust reverser components. In the deployed position, these doors extend outwardly from the nacelle to redirect the jet thrust.
The moveable thrust reverser components in each of the above-described designs are moved between the stowed and deployed positions by actuators. Power to drive the actuators may come from a dual output power drive unit (PDU), which may be electrically, hydraulically, or pneumatically operated, depending on the system design. A drive train that includes one or more drive mechanisms, such as flexible rotating shafts, may interconnect the actuators and the PDU to transmit the PDU's drive force to the moveable thrust reverser components.
The primary use of thrust reversers is, as noted above, to enhance the braking of the aircraft, thereby shortening the stopping distance during landing. Hence, thrust reversers are usually deployed during the landing process to slow the aircraft. Thereafter, when the thrust reversers are no longer needed, they are returned to their original, or stowed, position. Once in the stowed position, one or more locks are engaged to prevent unintended movement of the thrust reversers and/or actuators that move the thrust reversers.
Although the number of locks may vary, many thrust reverser systems include primary, secondary, and tertiary locks. Depending on thrust reverser system configuration, one or more primary locks may be coupled to one or more of the actuators, one or more secondary locks (or “brakes”) may be coupled to the PDU, and one or more tertiary locks may be coupled to one or more of the thrust reversers. Typically, the primary, secondary, and tertiary locks are electromechanical type of locks that are configured as “energized-to-unlock” and “de-energized-to-lock” devices. Thus, if no power is supplied to a lock, it will move to its locked position.
Thrust reverser actuation systems, such as the exemplary systems described above, are generally safe, reliable, and robustly designed. Nonetheless, thrust reverser systems may be subject to maintenance and repair processes. During such processes, power to the locks may not be available, thereby locking the actuators, PDU, and/or thrust reversers against movement. However, in some instances, it may be desired to move, for example, the PDU as part of a repair or maintenance process.
Hence, there is a need for a manual release mechanism for a thrust reverser actuation system electromechanical brake that will allow the brake to be disengaged, if desired, so that the PDU or other thrust reverser components can be moved. The present invention addresses at least this need.